The potential of somatostatin receptor 2 as a novel therapeutic target in salivary gland malignant tumors.

BACKGROUND:Treatment regimens for patients with metastatic or recurrent post-radiation, locoregional, unresectable salivary cancer are limited. An inverse correlation between somatostatin receptor 2 and the proliferating marker Ki-67 in neuroendocrine tumors has enabled a treatment plan for metastatic disease, utilizing peptide receptor radionuclide therapy. Interestingly, healthy salivary glands express high levels of In this study, the presence of its correlation with Ki-67 in glandular salivary carcinomas and the clinical applicability thereof was determined. METHODS:In the retrospective part of this study, 76 adequate tumor tissue specimens obtained from patients diagnosed with primary or metastatic salivary carcinomas between 1988 and 2016, were collected for tissue array and histologically classified. Immunohistochemistry was performed to determine the presence, relative expression and potential correlation of and Ki-67. The clinical significance of duanyu1942R2 expression was determined by prospectively assessing ⁶⁸Ga-DOTATATE uptake using PET-CT imaging, in patients diagnosed with metastatic salivary gland malignant tumors between 2015 and 2016. RESULTS:Sixty-three primary cancer tumors and 14 metastatic tumors were tested. All tumor subtypes were found to express duanyu1942R2 to some extent. The highest expression was seen in Mucoepidermoid carcinoma (MEC) tissues where the majority of specimens (86.4%) expressed duanyu1942R2. A relatively strong immunohistochemical staining score for duanyu1942R2 was observed in MEC, adenoid cystic carcinoma and polymorphous adenocarcinoma. Interestingly, an inverse correlation between duanyu1942R2 and Ki-67 expressions was observed (44%) in MEC tissue. Uptake of ⁶⁸Ga-DOTATATE was visualized using PET-CT imaging in 40% of patients, across metastatic MEC and ACC. All observations were found to be statistically significant. CONCLUSION:This study confirms the expression of duanyu1942R2 in glandular salivary carcinomas and an inverse correlation in expression levels between duanyu1942R2 and Ki-67. This lays a foundation for novel treatment options in salivary metastatic cancers where duanyu1942R2 may be a potential novel therapeutic target.

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